Round-robin tests during the last decades have convincingly shown that the common geometric modelling schemes where diffraction and scattering of sound are not adequately taken into account do not reliably predict sound fields in enclosed spaces. As a modelling tool in which the physical properties, i.e., the wave character, of sound is fully taken into account, TU Delft proposed the so-called WRW room acoustics modelling concept, derived from a modelling scheme commonly used in seismic exploration of oil and gas. The calculation schemes of the WRW model are based on the acoustic wave equation. Matrices R describe the local reflective properties of the room boundaries, matrices W specify the sound propagation to and from each boundary point. Goal of this subproject is to develop the WRW model from an attractive concept to an operational and efficient simulation tool. To realize this goal, an appropriate description of the reflective properties of the room boundaries should be determined, to be inserted in the matrices R. A library of such reflectivity properties for common boundary constructions has to be compiled, after determination of these properties by inverse extrapolation of microphone array measurement data. It also has to be investigated how the sound propagation between all boundary points, as described by the matrices W, can be calculated in a computationally most effective way. The end product of the subproject should be a simulation software package enabling the accurate and predictive simulation of 3D acoustic wave fields in complex enclosures, as a reference tool for research.